Surgical laser system microscope with separated ocular and objective lenses

ABSTRACT

The invention provides improved structures, systems, and methods for supporting the optical elements of a microscope relative to the optical train of a laser surgery system. As the field of view of the microscope is substantially fully determined by the position of the objective lens, the laser delivery optics and the microscope can be aligned with a target location of the patient&#39;s eye by accurately aligning just the objective lens with the delivery optics. By structurally separating the objective lens from the other optical components of the microscope, and by maintaining accurate alignment between the objective lens and the laser delivery optics with a simple, tight-tolerance support structure, the remaining optical components of the microscope can be allowed to “float” relative to the objective lens with a looser-tolerance without degrading the operator&#39;s ability to align, observe, and optically direct an ophthalmic laser procedure.

CROSS-REFERENCES TO RELATED APPLICATIONS

[0001] The present application is a divisional patent application of andclaims the benefit of priority from U.S. patent application Ser. No.09/105,073 filed Jun. 26, 1998, the full disclosure of which isincorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] The present invention is generally related to microscope systemsused to observe and/or direct laser eye surgery. In particular, thepresent invention provides devices, systems, and methods forstructurally supporting the optical elements of a microscope relative tothe optical train of the laser delivery system. The present invention isparticularly useful for optically observing laser surgical proceduressuch as photorefractive keratectomy (PRK), phototherapeutic keratectomy(PTK), laser assisted in situ keratomileusis (LASIK), or the like.

[0003] Ophthalmic laser surgery and other ophthalmic procedures areoften performed by a laser after optically aligning the laser with theeye using a microscope. While it may be possible to make use of lasershaving other wavelengths, known laser eye surgery procedures generallyinclude an ultra-violet or modified frequency infrared laser to remove amicroscopic layer of stromal tissue from the eye's cornea to alter itsrefractive power. In one application, the laser removes a selectedportion of this corneal tissue in order to correct refractive errors ofthe eyes. Laser ablation results in photodecomposition of the cornealtissue, but generally does not cause significant thermal damage toadjacent and underlying tissues of the eye. The irradiated molecules arebroken into smaller volatile fragments photochemically, directlybreaking the intermolecular bonds. The microscope is often used toobserve the treatment during and/or after the ablation, as well as toalign the ablation with the eye.

[0004] Laser ablation procedures can remove the targeted stroma of thecornea to change the cornea's contour for varying purposes, such as forcorrecting myopia, hyperopia, astigmatism, and the like. While a varietyof approaches and systems have been described for controlling thedistribution of tissue ablation across the cornea, including masks,fixed and movable apertures, controlled scanning systems, eye movementtracking mechanisms, and the like, most laser eye systems include amicroscope to aid the surgeon in aligning the patient's cornea with thelaser system, and to allow the surgeon to optically monitor or verifythat the targeted portion of the stroma is removed as intended.

[0005] Known laser eye surgery systems have generally included fairlystandard microscope structures. The focus and field of view of aconventional microscope is often controlled by shifting the specimen tobe viewed relative to the microscope structure. To target the field ofview of microscopes used for laser eye surgery upon the patient's eyeand allow observation of the laser beam delivery, these microscopes areinstead often shifted in three dimensions relative to the supportstructure of the laser beam delivery system. Both positioning andstability of the microscope are tightly controlled, since anydisplacement of the microscope structure from proper alignment with thelaser delivery location is magnified by the magnification of themicroscope.

[0006] While these known laser eye surgery systems are quite effective,the cost and complexity of the microscope positioning and supportstructure are significant disadvantages. To provide adequate positioningand stability of the microscope relative to the laser delivery opticaltrain, known laser eye surgery systems typically include a microscopeadjustment structure having parts machined to tight tolerances. Thisadjustment structure often accommodates travel of the microscope in X,Y, and Z directions with a high degree of accuracy. These microscopeadjustment mechanisms add significantly to the overall costs of thelaser eye surgery system.

[0007] In light of the above, it would be desirable to provide improvedlaser eye surgery systems, devices, and methods. It would beparticularly desirable to provide enhanced techniques for structurallysupporting the microscope relative to the other components of the lasersystem. It would further be desirable if these improvements could beprovided with less complexity, greater reliability, and a lower costthan known laser surgery/microscope support systems.

SUMMARY OF THE INVENTION

[0008] The present invention provides improved structures, systems, andmethods for supporting the optical elements of a microscope relative tothe optical train of a laser eye surgery system. The present inventiongenerally takes advantage of a surprising characteristic of manymicroscopes: the field of view of the microscope can be substantiallyfully determined by the position of the objective lens. As a result, thefield of view of the microscope can be fixed by accurately positioningjust a portion of the many optical components of the microscope. Inother words, the laser delivery optics and the microscope can be alignedwith a target location of the patient's eye by accurately aligning justthe objective lens with the delivery optics. By structurally separatingthe objective lens from the other optical components of the microscope,and by maintaining accurate alignment between the objective lens and thelaser delivery optics with a simple, tight-tolerance support structure,the remaining optical components of the microscope can be allowed to“float” relative to the objective lens with a looser tolerance withoutdegrading the operator's ability to align, observe, and optically directa procedure, particularly when using a microscope having a Galileanmagnification changer.

[0009] In a first aspect, the present invention provides a laser eyesurgery system for resculpting a cornea of a patient. The systemcomprises a laser to produce a laser beam. Laser delivery optics areoptically coupled to the laser so as to direct the laser beam toward thecornea of the patient. The laser directed by the laser delivery opticswill generally alter refraction of the cornea. An optics supportstructure supports at least a portion of the delivery optics.

[0010] The laser eye surgery system further includes a microscope havingan eyepiece, an objective lens, and a microscope body. The microscopebody is attached to the optics support structure, and will directlysupport the eyepiece. Unconventionally, the laser optics supportstructure directly holds the objective lens in alignment with at least aportion of the delivery optics.

[0011] By supporting the objective lens and laser delivery optics with acommon structural support system, the present invention can ensurealignment between the entire microscope and the treatment site.Advantageously, an off-the-shelf microscope can be modified for use inthe present invention by removing its objective lens and mounting themicroscope body and eyepiece on a mounting pad of the optic supportstructure. Even though the resulting positioning tolerance of theeyepiece of the microscope may be significantly looser than thepositioning tolerance of the objective lens relative to the deliveryoptics, alignment is maintained between the field of view and treatmentsite. The laser beam will often be substantially coaxial with theobjective lens, the objective lens often being disposed between theeyepiece of the microscope and a partially reflective mirror or otherbeam splitting structure. The off-the-shelf microscope will preferablycomprise a binocular microscope having a Galilean magnification changer.

[0012] The optics support structure will generally restrain theobjective lens of a microscope in fixed lateral alignment with atreatment axis of the laser beam. In production models, the objectivelens will also be axially affixed relative to the treatment axis.Alternatively, particularly in pre-production development models of thepresent laser system, the axial position of the objective lens may beadjustable to determine the proper alignment between the field of viewof the microscope and the laser delivery optics. Once this axialalignment has been determined, a variable axial positioner may beremoved and replaced with a fixed spacer.

[0013] In another aspect, the present invention provides a method forfabricating a laser eye surgery system. The method comprises providing amicroscope having an eyepiece supported relative to a mounting surfaceby a microscope body. An objective lens of the microscope, together withlaser delivery optics, are mounted on a delivery optics supportstructure so that the optics support structure maintains alignmentbetween the delivery optics and the objective lens with a firsttolerance. The optics support structure includes a mounting pad, and themicroscope body is attached to that mounting pad so as to align theeyepiece with the objective lens. The eyepiece is aligned with a secondtolerance which is looser than the first tolerance.

[0014] Advantageously, the lateral alignment of the objective lens and atarget axis of the delivery optics may be fixedly restrained by theoptics support structure. An axial position of the objective lens mayinitially be determined using an adjustable positioner of the opticsupport structure. Once this axial position is determined, theadjustable positioner can be replaced with a fixed spacer to immovablyrestrain an objective lens at the determined axial position. This allowsthe field of view of the microscope to be permanently set at the desiredposition, and avoids having to resort to a complex, tight-tolerance, andexpensive adjustment system for translating the microscope relative tothe delivery optics in three dimensions. Fixing of the objective lens(and thereby the field of view of the microscope) also increases theefficiency of the system by eliminating the previously required steps ofaligning the microscope with the targeted corneal tissues. Instead, thefield of view of the microscope remains aligned with the treatment axisof the laser delivery optics when the cornea is positioned, generally bymoving the entire patient on a moveable operating table.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 is a perspective view of a laser eye surgery systemaccording to the principles of the present invention, in which thestructure supporting the microscope and laser delivery optics has beenremoved to more clearly show the optical components.

[0016]FIG. 2 is a perspective view of the laser delivery optics ofanother laser eye surgery system, including several of the opticalsub-systems of the laser and the objective lens of the microscope.

[0017]FIG. 3 is a perspective view of a microscope together with andsome of the laser delivery optics.

[0018]FIG. 4 is a schematic illustration showing how the optics supportstructure maintains a fixed alignment between the objective lens andlaser delivery optics, and also illustrates how the remaining componentsof the microscope are allowed to float at a looser tolerance.

[0019]FIG. 5 is a front view of a microscope showing a portion of thelaser delivery optics of another laser eye surgery system.

[0020]FIG. 6 is an exploded side view of the microscope body and opticsupport structure.

[0021]FIG. 7 is a detailed view showing the mounting of the microscopebody to the optics support structure, and also illustrating a fixedspacer which axially positions the objective lens.

[0022]FIG. 8 is a cross-sectional view of an adjustable positioner todetermine the desired axial position of the objective lens prior tofabricating the fixed spacer of FIG. 7.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS

[0023] The present invention is generally directed to structures,systems, and methods for fabricating and supporting a microscope of alaser eye surgery system. The techniques of the present inventiongenerally involve structurally separating the objective lens of themicroscope from the microscope body. The separate objective lens isdirectly supported by the same structural frame work that holds theoptical elements of the laser delivery system. The focus and field ofview of a conventional microscope having a Galilean magnificationchanger is substantially determined by the position and orientation ofthe objective lens. As the desired field of view for a microscope usedin laser eye surgery can be predetermined to allow observation of thedelivery of the laser beam at the cornea, this allows the objective lensto be fixed in alignment with the laser delivery optics.

[0024] In general, positioning and stability of a microscope relative tothe laser delivery system is very important. Any displacement of themicroscope from the center of the laser delivery will be magnified bythe microscope magnification setting in the image viewed through themicroscope. To obtain the desired positioning and accuracy andstability, known laser eye surgery systems generally make use ofexpensive machined parts to allow displacement of the entire microscopein five degrees of freedom relative to the laser delivery site. Byinstead mounting the objective lens of the microscope to the supportstructure holding the laser delivery optics, the focus and field of viewof the microscope can remain substantially aligned with the opticaltrain for the laser beam. The positioning accuracy of the remainingoptical components of the microscope can then be allowed to float with alooser tolerance in the X, Y, and Z directions. Despite minor variationsin the positioning of the eyepiece (and other optical components of themicroscope) relative to the objective lens, the focal plane and field ofview of the microscope will remain aligned with the laser beam so longas the objective lens is firmly affixed relative to the laser deliveryoptics. Hence, the present invention effectively provides structuralfixation of the microscope without having to provide all the complex andexpensive microscope adjustment mechanisms generally found supportingthe microscopes of laser eye surgery systems.

[0025] The present invention may find applications in a variety ofsettings. The invention generally allows alignment of a therapeutic orinterventional laser beam with the field of view of a microscope, andmay therefore be useful for a variety of laser surgeries, cellularmanipulations, and the like. However, the most immediate application forthe present invention will be in the field of laser eye surgery. As thestructural system of the present invention maintains alignment betweenthe microscope field of view and the laser delivery optics, theinvention allows photoablation of selected portions of the corneawithout having to realign the microscope and laser delivery optics foreach procedure, daily, or at regular maintenance intervals. Hence, thepresent invention will have benefits for photorefractive keratectomy(PRK including procedures to correct hyperopia, myopia, astigmatism, orany combination thereof), phototherapeutic keratectomy (PTK), laserassisted in situ keratomileusis (LASIK), and the like.

[0026] Referring now to FIG. 1, a laser eye surgery system 10 includes alaser 12 that produces a laser beam 14. Laser 12 is optically coupled tolaser delivery optics 16, which direct laser beam 14 to an eye of apatient P. A delivery optics support structure (see FIGS. 4-7, not shownhere for clarity) extends from a frame 18 supporting laser 12. Amicroscope 20 is mounted on the delivery optic support structure.

[0027] Laser 12 generally comprise an excimer laser, ideally comprisingan argon-fluorine laser producing pulses of laser light having awavelength of approximately 193 nm. Laser 12 will preferably be designedto provide feedback stabilized fluence of 160 mJoules/cm2 at thepatient's eye, as delivered via delivery optics 16. The presentinvention may also be useful with alternative sources of radiation ofany wavelength, particularly those adapted to controllablyphotodecompose the corneal tissue without causing significant damage toadjacent and/or underlying tissues of the eye.

[0028] Laser 12 and delivery optics 16 will generally direct laser beam14 to the eye of patient P under the direction of a computer 22.Computer 22 will generally selectively expose portions of the cornea tolaser pulses of laser beam 14 so as to effect resculpting of the corneaand alter the refractive characteristics of the eye.

[0029] Laser beam 14 may be tailored to produce the desired resculptingusing one or more variable apertures (such as a variable iris andvariable width slit as described in U.S. Pat. No. 5,713,892, the fulldisclosure of which is incorporated herein by reference), by varying thesize and offset of the laser spot from the axis of the eye (as describedin U.S. Pat. No. 5,683,379, and also described in co-pending U.S. patentapplication Ser. No. 08/968,380, filed Nov. 12, 1997, the fulldisclosures of which are incorporated herein by reference), by scanningthe laser beam over the surface of the eye and controlling the numberpulses and/or dwell time (as described by U.S. Pat. No. 4,665,913, thefull disclosure of which is incorporated herein by reference), usingmasks in the optical path of laser beam 14 which ablate to varying theprofile of the beam incident on the cornea (as described by U.S. patentapplication Ser. No. 08/468,895, filed Jun. 6, 1995, the full disclosureof which is incorporated herein by reference), or the like. The computerprograms and control methodology for each of these resculptingtechniques is well described in the patent literature.

[0030] Additional optical components may also be included in the opticalpath of laser beam 14, such as integrators to spatially and/ortemporally control the distribution of energy within the laser beam (asdescribed in U.S. Pat. No. 5,646,791, the disclosure of which isincorporated herein by reference), and the like. Similarly, otherancillary components of the laser surgery system which are not necessaryto an understanding of the invention, such as an ablation effluentevacuator/filter, conventional computer sub-system components includingthe keyboard, the display, monitor, and program and data storage media,will often be provided, as should be understood by those of skill in theart.

[0031] The head of patient P will be firmly supported on, and preferablyrestrained by an operating table 24. Positioning of the eye relative tothe laser delivery optics is generally effected by movement of theoperating table 24. Hence, operating table 24 is supported by anactuation mechanism 26 which can move the patient to vertically andhorizontally position the cornea of the eye at a predetermined targettreatment site. Alternatively, microscope 20 and at least a portion oflaser delivery optics 16 may move in unison to align laser beam 14 withthe cornea. When the laser delivery optics are to be moved, theobjective lens of microscope 20 will preferably remain affixed relativeto at least a portion of the laser optical train adjacent the eye so asto maintain alignment between the microscope field of view and the lasertreatment site.

[0032] Referring now to FIG. 2, several of the components of deliveryoptics 16 are illustrated with adjacent sub-systems of the laserdelivery system. After passing a laser energy detector 28, laser beam 14from laser 12 is directed through an aperture wheel 32. The laser beamthen continues to a beam splitter 34 which directs laser beam 14 along atreatment axis 36 to eye E. To help the patient maintain eye E in theproper orientation, the patient will preferably maintain focus upon atarget of patient fixation system 38. An alignment system 40 helps thelaser system operator properly position the patient for treatment. Areticle 42 can be projected into the microscope as shown. Illuminationof the eye can be provided using a ring illuminator 44 and obliqueilluminators 46, while aspiration of photodecomposition debris can beprovided by aspiration nozzle 48. It should be noted that the specificarrangement of optical elements and support structure of the illustratedlaser eye surgery systems may vary somewhat between the figures.

[0033] Of particular importance for the present invention, an objectivelens 50 of microscope 20 (see FIG. 1) is disposed in close proximity tothe downstream elements of laser delivery optics 16. Objective lens 50will preferably have an axis 51 coaxially aligned with treatment axis36. Beam splitter 34, which will typically be in the form of a partiallyreflective mirror so as to redirect laser beam 14, will transmit visiblelight provided by obliques 46 and ring illuminator 44 as scattered byeye E to the objective lens, so that the eye can be imaged withouthaving to transmit the high powered laser beam through the objectivelens of the microscope.

[0034] The arrangement of the optical components of delivery optics 16adjacent microscope 20 is seen most clearly in FIG. 3. Mirrors 30 areadjustably mounted to allow alignment of laser beam 14 relative to thetreatment pattern. Microscope 20 makes use of, but is largelystructurally separated from objective lens 50. Along with objective lens50, microscope 20 also includes a microscope body 52 and a pair ofbinocular eye pieces 54. An optical beam splitter 53 is disposed betweenbody 52 and eye pieces 54 to allow a video system to be coupled to themicroscope so that assistants may observe the procedure and the like.

[0035] Microscope body 52 supports a Galilean magnification changer 56.Such Galilean magnification changers typically allow incrementaladjustment of the magnification of the microscope by moving one or morelens sets into or out of the optical path between objective lens 50 andeye pieces 54 so as to alternatively increase, decrease, or have noeffect on the magnification provided by the microscope.

[0036] Microscopes having Galilean magnification changers arecommercially available from LEICA of Switzerland; from Zeiss of Germany;and others. In general, these commercially available microscopes areprovided with an integral objective lens supported directly by themicroscope body. Such off-the-shelf microscopes may be modified for useaccording to the present invention by removing the objective lens, theymay be ordered from the supplier without the objective lens, or they maybe specially fabricated for use in the present laser system, all withinthe scope of the present invention. In general, these microscopesprovide three or five magnification settings as determined by rotatingmagnification changer 56. Adjustments are often provided so as toaccommodate a few diopters of myopia or hyperopia in each eye of theperson viewing the laser eye surgery procedure through the microscope.The optical components of microscope 20 are illustrated in FIG. 4, and aparticularly preferred microscope for modification and use within thepresent laser eye surgery system is commercially available from LEICA ofHeerbrugg, Switzerland under Model No. MS5.

[0037] The structural support arrangement of the present invention canbe understood most easily with reference to FIG. 4. Delivery optics 16(including beam splitter 34) are held in alignment with eye E by adelivery optics support structure 60. To maintain alignment between theeye and the field of view of microscope 20, objective lens 50 is alsodirectly supported by delivery optics support structure 60. Eye pieces54 (and the other optical components of microscope 20) are supported bymicroscope body 52 in a conventional manner. To maintain alignmentbetween eye pieces 54 and objective lens 50, microscope body 52 includesa mounting surface 62 which engages a mounting pad 64 of delivery opticssupport structure 60.

[0038] As objective lens 50 is directly mounted to delivery opticssupport structure 60, alignment between the objective lens and laserdelivery optics 16 (and hence to laser beam 14) can be maintained to avery tight tolerance. Preferably, objective lens 50 is positionedrelative to delivery optics 16 within a tolerance of about 0.5 mm ormore, the objective lens ideally being positioned relative to thedelivery optics within a tolerance of 0.2 mm.

[0039] As described above, the accurate positioning of objective lens 50relative to laser delivery optics 16 ensures that the field of view ofmicroscope 20 will be properly positioned relative to the cornealtreatment site. As a result, the other optical components of microscope20 (including eye pieces 54) can be allowed to float in the X, Y, and Zdirections with a relatively loose tolerance support structure. Hence,eye pieces 54 may be supported by microscope body 52, mounting surface62, mounting pad 64, and delivery optics support structure 60 with atolerance of about ±2.5 mm relative to objective lens 50. The totallateral tolerance, or X and Y displacement, of the optical componentssupported by microscope body 52 relative to the corneal treatment siteon eye E will actually be determined by the characteristics of objectivelens 50. More specifically, a high quality image of the cornealtreatment site can be provided through microscope 20 so long asobjective lens 50 is aligned laterally with the treatment axis, and solong as the other optical components of microscope 20 remain alignedwithin a distortion-free zone 66 of objective lens 50. Hence, allowablelateral displacement of these optical components can be enhanced byproviding an objective lens which has a distortion-free zone that issignificantly larger than would be required if objective lens 50 wereaffixed directly to the microscope body. In the exemplary embodiment,objective lens 50 comprises a 50.0 mm diameter lens having a focallength of 300 mm, the objective lens being formed of two adjacent lensesand coated with a broadband anti-reflective coating.

[0040] An exemplary structural interface between microscope 20 anddelivery optics support structures 60 is illustrated in more detail inFIGS. 5-7. Rather than occupying the standard position 68 for anobjective lens affixed directly to microscope body 52, objective lens 50is fastened to delivery optics support structure 60 as shown. Afterremoval of its standard objective lens, microscope 20 is mounted todelivery optics support structure 60 by fastening mounting surface 62 ofthe microscope to mounting pad 64 of the support structure withfasteners 70.

[0041] Although it is possible to accurately determine the properlateral position of objective lens 50 prior to fabrication of deliveryoptics support structure 60 and assembly of the microscope and supportstructure together, calculation of the axial position of the objectivelens relative to the corneal treatment site is somewhat moreproblematic. Empirical calculations of the focal plane of the imageviewed through microscope 20 can be somewhat misleading, so that thedesired position for objective lens 50 may benefit from slightadjustments from those calculated. Nonetheless, once the proper axialposition has been determined, reliable focal plain positioning should bepossible by repeating the lessons learned during development. Therefore,the present invention provides a variable axial positioner 72 asillustrated in FIG. 8.

[0042] Objective lens 50 can be axially positioned using variablepositioner 72 by affixing the variable positioner to delivery opticssupport structure 60 in place of a fixed spacer 74. This allowsadjustment to the axial position of the objective lens 50 within theassembled microscope and laser system. Once the proper axial position isdetermined, the dimensions of fixed spacer 74 can be set. Productionversions of the laser system will then include fixed spacer 74 affixedto delivery optics support structure 60 as shown in FIGS. 6 and 7. As aresult of this development process, the focal plain of microscope 20should be immediately and repeatably positioned at the corneal treatmentsite upon assembly of the surgery system, without requiring translationand adjustment of the entire microscope structure.

[0043] While the exemplary embodiment of the present invention has beendescribed in some detail, by way of example and clarity ofunderstanding, a variety of modifications, adaptations, and changes willbe obvious to those of skill in the art. For example, the presentinvention may be used with microscopes having a single ocular lensrather than the binocular structures illustrated and described herein.Additionally, the beam splitter may redirect the optical image whiletransmitting the laser beam, or may be pivotally mounted to scan thelaser beam across the cornea about the treatment axis. Hence, the scopeof the present invention is limited solely by the appended claims.

What is claimed is:
 1. A laser eye surgery system for resculpting acornea of a patient, the system comprising: a laser to produce a laserbeam; laser delivery optics optically coupled to the laser so as todirect the laser beam toward the cornea of the patient for alteringrefraction of the cornea; an optics support structure supporting atleast a portion of the delivery optics; and a microscope having one ormore eyepiece, an objective lens, and a microscope body, the microscopebody attached to the optics support structure and directly supportingthe eyepiece, the optics support structure directly holding theobjective lens in alignment with the at least a portion of the deliveryoptics.
 2. The laser system of claim 1, wherein the optics supportstructure has a microscope mounting pad, wherein the microscope body hasa mounting surface that engages the mounting pad of the optics supportstructure, and wherein the one or more eyepiece is coupled to theobjective lens by the engaged mounting pad and mounting surface.
 3. Thelaser system of claim 2, wherein the optics support structure holds theobjective lens in alignment with the at least a portion of the deliveryoptics with a first tolerance, and wherein the microscope body, engagedmounting pad, mounting surface, and optics support structure support theone or more eyepiece relative to the objective lens with a secondtolerance which is looser than the first tolerance.
 4. The laser systemof claim 1, wherein the objective lens defines a lens axis, wherein thedelivery optics direct the laser beam toward the cornea along atreatment axis, and wherein the optics support structure restrains thelens axis of the objective lens in fixed lateral alignment with thetreatment axis.
 5. The laser system of claim 4, wherein the opticssupport structure includes an axial positioning surface that immovablyaffixes the objective lens axially along the treatment axis.
 6. Thelaser system of claim 5, wherein the axial positioning surface isdisposed on a spacer, and further comprising a variable axialpositioner, the variable axial positioner movably positioning theobjective lens along the treatment axis when the variable axialpositioner is installed in the optics support structure in place of thespacer.
 7. The laser system of claim 1, wherein the microscope bodymovably supports a binocular lens system and a Galilean magnificationchanger.
 8. The laser system of claim 1, wherein the eyepiece has afield of view extending toward the objective lens, and wherein theobjective lens has a substantially distortion free zone, the distortionfree zone of the objective lens being larger than the field of view ofthe eyepiece to accommodate lateral misalignment between the eyepieceand the objective lens.
 9. The laser system of claim 1, furthercomprising a beam splitter disposed in an optical path of the laser beamand in an optical path of the microscope so as to separate the opticalpaths, wherein the objective lens is disposed between the eyepiece andthe beam splitter along the optical path of the microscope.
 10. A lasereye surgery system for resculpting a cornea of a patient, the systemcomprising: a laser to produce a laser beam adapted to photoablate aportion of the cornea; laser delivery optics optically coupled to thelaser so as to direct the laser beam toward the cornea of the patientfor selectively resculpting the cornea; a microscope having an eyepiece,an objective lens, and a microscope body, the microscope body supportingthe eyepiece and having a mounting surface; a delivery optics supportstructure supporting at least a portion of the delivery optics, the atleast a portion of the delivery optics directing the laser beam towardthe cornea along a treatment axis, the optics support structure having amicroscope mounting pad engaging the mounting surface, the opticssupport structure holding the objective lens in immovable lateralalignment with the at least a portion of the delivery optics with afirst tolerance, the microscope body, optics support structure, andengaged mounting pad and mounting surface supporting the eyepiecerelative to the objective lens with a second tolerance which is looserthan the first tolerance.